The Old Farmer’s Almanac lists July 3, incorrectly according to some, as the onset of Dog Days. We’ve all heard of Dog Days, but where does it come from?
The Romans referred to the dog days as diēs caniculārēs and associated the hot weather with the star Sirius. They considered Sirius to be the “Dog Star” because it is the brightest star in the constellation Canis Major (Large Dog).
The Dog Days originally were the days when Sirius rose just before or at the same time as sunrise (heliacal rising), which actually takes place the first part of August. The Romans sacrificed a brown dog at the beginning of the Dog Days to appease the rage of Sirius, believing that the star was the cause of the hot, sultry weather.
Many people believe the phrase is in reference to the conspicuous laziness of domesticated dogs during the hottest days of the summer.
July 3, 2018 the Earth is also at aphelion or its closest to the sun.